1. FIELD OF THE INVENTION
This invention relates to kinematic fixturing in optical systems, particularly mounting optical components under preload so as to minimize deformation during thermal expansion and contraction thereof.
2. THE PRIOR ART
In an optic system, components such as lenses or mirrors can thermally distort, impairing the accuracy of the transmitted and/or reflected beam. Thus if a lens or mirror distort due to heating by a laser beam, 1) the beam can be transmitted at the Wrong size, 2) the beam can be directed off target and 3) the so-transmitted beam undergoes diminished optical quality of wavefront.
In the prior art, considerable attention has been directed toward providing passages in e.g., mirrors, for cooling same with water in a range of 67.degree. to 70.degree. F. so as to avoid or minimize mirror (or lens) distortion due to heating by reflective contact with a laser beam.
Despite such efforts however, portions of the mirror surface are heated by a laser beam above the desired cooling range resulting in expansion and thermal distortion thereof. This is in part due to the mounting of such mirror to a metal backing member, which then mounts to a metal frame (e.g., by metal screws). For examples of such metal backed and mounted mirrors, see Mostel U.S. Pat. No. 3,588,232 (1971) and Eitel U.S. Pat. No. 4,029,400 (1977). These mirrors can be mechanically adjusted in two planes or directions, which adjustments are thereafter fixed, to hold the respective mirrors in place.
Though the metal backing mirror and/or frame be of high quality, e.g., of titanium, despite elaborate mounting systems and the above-noted, water-cooling thereof, mirror distortion upon contact with high temperature laser beams has persisted. Accordingly, for purposes of the present invention, attention has turned to backing such mirrors with ceramic material such as silicon carbide (SiC). Such ceramic has a coefficient of thermal expansion of less than that of molybdenum, has greater stiffness and is more stable against the heat of a laser beam. However ceramics has special mounting problems e.g., to metal frames, in that screw threads induced into such ceramic backing or mounting, are brittle and break or crumble with repeated screw insertions therein. Also some thermal distortion persists even with a ceramic backing and there has been a need to find a mounting for such ceramic backed mirrors that would be more durable and otherwise overcomes the above prior art shortcomings.
There has now been discovered a means for mounting such ceramic backed mirrors that is of a more permanent nature and that permits thermal expansion and contraction of such ceramic optic components so as to lessen or minimize optical distortion thereof and achieve an optical stability not previously seen.